1. Field of the Invention
The present invention generally relates to an apparatus and process for producing biocoke usable as a substitute fuel for coal coke from biomass as a raw material attributed to photosynthesis.
2. Description of the Related Art
In recent years, considering global warming which the increase in carbon dioxide level is contributing to and the predicted depletion of fossil fuel, biomass has attracted attention as a renewable clean energy source.
Biomass generally means a renewable and biological organic resource excluding fossil fuels. By treating this biomass to carbonized gas, valuable resources such as heat, electricity, or a carbonized object can be obtained and biomass as waste is processed, which helps in cleaning up the environment. Moreover, it is thought that as biomass is an organic matter, carbon dioxide caused from combustion of the biomass comes from carbon dioxide absorbed from the air by photosynthesis during the growth of biomass, thus causing no increase in carbon dioxide level in the air. This is called carbon neutral. Therefore, utilization of biomass is encouraged.
On the other hand, due to fast growing demand for iron and steel in China, the cost of producing coal cokes is running up and significantly weighing on businesses of cast metal and iron makers in Japan. Therefore, solidified fuel with high hardness to replace a portion of coal cokes in manufacturing cast metal or iron is longed for, which can lower the fuel cost and suppresses the rise in carbon dioxide level in the air via the carbon neutral characteristic of biomass.
As a process to treat biomass to fuel, a production method of biomass water slurry disclosed in Patent Reference 1 (JP2003-129069A) and a method of converting raw garbage and sewer sludge into fuels disclosed in Patent Reference 2 (JP3613567B) are known.
However, neither of the inventions disclosed in Patent References 1 and 2 relates to the art of converting biomass into solidified fuel and cannot be used as a substitute of coal cokes.
As a method for converting biomass into solid fuels, a pellet production process is disclosed in Patent Reference 3.
However, according to the method disclosed in Patent Reference 3 (JP52-101202A), a produced pellet has higher moisture content and does not have enough heat value to substitute for coal cokes. The produced pellet holds airspace therein, causing air (oxygen) to disperse within the pellet and shortening the combustion time, and among pulverized biomass no binding exists, causing the pallet to have insufficient hardness.
Thus, it is difficult to use the produced pellet to substitute for coal cokes.
Moreover, as another art of converting biomass into solid fuel, there are an art of shredding into small pieces and carbonizing a raw material (Patent Reference 4: JP2004-43517A), an art of producing a solid fuel having higher volume energy density and weight energy density than those of charcoal in a high energy yield (Patent Reference 5:JP2003-213273A), and an art of producing biomass semi-carbonized compressed fuel which improves transportability of ligneous biomass energy (Patent Reference 6: JP2003*206490A). The solid fuels disclosed in Patent References 4 to 6 do not have very high heat value to substitute for coal cokes, or sufficient hardness, and thus it is difficult to substitute coal cokes with those solid fuels.